The present invention relates to the field of appliances intended to furnish hot water and/or steam for different operations such as the preparation of hot beverages, cleaning, pressing or cooking. The invention concerns more particularly the structure and operation of a water heater or heating unit, arranged for example, in a coffee maker of the filter of espresso type. Other appliances such as steam generators, pressing irons or steam cookers are equally concerned and do not fall outside of the framework of the present invention.
It is already known, and particularly from the document EP-A-0432460 to make water heaters, for hot beverage machines, in a particular form, in order to transfer and heat the water with an improved efficiency. The water heater described in this prior art document comprises a heating element in thermal communication with a water circulation pipe. The heating element and the pipe have a form substantially in a U with vertical inlet and outlet portions and an intermediate portion which is slightly inclined and rises relative to the horizontal in the direction of water circulation. In addition, the heating element comprises four heating zones which are differentiated and distributed along the water circulation pipe. Such a conception permits in particular evacuation toward the outlet portion of vapor bubbles while preventing their return toward the inlet portion of the pipe.
The drawbacks of a water heater such as described in the document EP-A-0432460 is on the one hand the impossibility of utilizing said water heater to produce hot water or vapor as desired by the user and on the other hand a complexity of fabrication or production which increases its cost.